Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations at all, the description carries the full burden and does well: it discloses that the call is paid ($0.01 USDC on Base or Solana), that no account or API key is needed, that failed calls are not charged, and that data comes from DefiLlama. It stops short of rate limits, latency, or result freshness/pagination behaviour.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with 'Paid.' then the capability, followed by the return fields and commercial terms; every sentence carries information. The phrasing is telegraphic but not padded, and the URL is placed last where it belongs.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 3-optional-parameter read tool with no output schema and no annotations, the description covers what is returned, the data source, and the payment constraints, which is most of what an agent needs. The main residual gap is response shape/paging, which is only hinted at by the field list.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so sort, limit, and min_tvl_usd (with defaults) are already fully documented in the schema. The description adds nothing about these controls – no guidance on sensible sort/limit combinations or how min_tvl_usd interacts with result counts – so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: live DeFi yield pools for the fluid-lending protocol, with the fields returned (APY, TVL, 7d APY change) named explicitly. The protocol name in the tool name plus the description's 'fluid-lending' phrase separates it from chain-level and other protocol siblings, but the description never explains the boundary versus near-neighbours like fluid-dex or fluid-lite.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied by the tool name and the resource named – an agent can infer 'call this when you want fluid-lending pool yields'. There is no explicit when-to-use, no exclusion versus buy_yields_chain_* or buy_yields_protocol_fluid-dex, and no prerequisites such as wallet/payment setup beyond the price statement.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.